Field of the Invention
The present invention relates to a printed wiring board for package-on-package (POP).
Description of Background Art
Japanese Patent Laid-Open Publication No. 2009-135398 describes a printed wiring board for package-on-package. The printed wiring board for package-on-package in Japanese Patent Laid-Open Publication No. 2009-135398 includes a lower substrate to which a printed wiring board is attached, an upper substrate to which a package substrate is mounted, and an interposer that is interposed between the lower substrate and the upper substrate and has a metal post. The lower substrate has a pad that is formed on a surface on one side of the lower substrate for connecting to the upper substrate, and a pad that is formed on a surface on the other side of the lower substrate for connecting to a printed wiring board. The upper substrate has a pad that is formed on a surface on one side of the upper substrate for connecting to the lower substrate, and a pad that is formed on a surface on the other side of the upper substrate for connecting to a package substrate. The pad for connecting to the lower substrate and the pad for connecting to the upper substrate are electrically connected by the metal post. Further, an IC chip is mounted between the lower substrate and the upper substrate. The entire contents of this publication are incorporated herein by reference.